The disclosure relates to a wireless transmission device and a wireless communication device, and can be particularly applied to a wireless transmission device and a wireless communication device using a plurality of class-D amplifiers.
In recent years, there has been an increased demand for computer devices and mobile terminals using wireless communications such as Bluetooth (registered trademark) that is one of short-range wireless communication standards for digital devices. In addition, there has been a request of forming a wireless transmission device on one chip to be mounted in a wearable device, and wireless transmission devices are increasingly mounted into semiconductor devices such as microcomputers or SoC (System on a Chip). It has been considered to use a class-D amplifier as a power amplifier in a wireless transmission device adapting to the Bluetooth standard.
An example of a technique using a class-D amplifier as a power amplifier is proposed in, for example, “Wei-Han Yu et al., “A High-Voltage-Enabled Class-D Polar PA Using Interactive AM-AM Modulation, Dynamic Matching, and Power-Gating for Average PAE Enhancement”, IEEE TRANSACTION ON CIRCUIT AND SYSTEMS-I: REGULAR PAPERS, vol. PP, Issue: 99, pp. 1-14, 31 May 2017” (hereinafter, referred to as Yu Literature). With reference to FIG. 3 of Yu Literature, in order to control a transmission electric power (Pout), the number of class-D amplifier units that are coupled in parallel and perform a class-D amplifying operation is adjusted. The class-D amplifier units that are not allowed to perform a class-D amplifying operation become an OFF state by internal switch control, and become an open (Hi-Z) state when seen from the VD end. Impedance (ZDMN) when seeing a matching unit (DMN) from the VD end is adjusted by only a capacitance CDMN.